A lady in my church has several children all in their adult years now. Two of her daughters live in state and her son serves in the armed forces overseas. One of her daughtes in particular is what people would call "not serving the Lord". That means she's not actively following the teachings of Jesus Christ nor cares to at this time. For a mother who raised her kids to do so, that is heart-breaking but she has nothing but love for her nonetheless.
One day this particular daughter called. She was hoping to buy a house and apparently it was a long shot. She was hoping that she would be able to buy this house. So, she understands her mother believes in, hopes in and trusts God and actually talks to him. She calls her mother and says, "Mom, do your thing." In other words, she was saying, "Mom, pray for me." To make a long story short, she got the house, mom feels gratified and God gets the credit.
I share this with all of the moms (and dads) out there with wayward kids. Keep doing your thing! Don't ever stop praying. Don't stop believing. Don't stop loving them. So long as your kids know that they can call you at any time to pray for anything, it's a good thing. And if they are calling for prayer as they walk in their way without God, they are actually admitting that what you are doing is relevant. If it wasn't they wouldn't ask you for it.
This particular day one wayward daughter asked for prayer for a house. It worked. Who knows what they may ask for prayer for next. It just might be the thing that changes their life!
Keep doing your thing.